Method for manufacturing an airfoil

ABSTRACT

A method for manufacturing an airfoil includes casting the airfoil around a core and creating a hole through a surface of the airfoil with a water jet. The method further includes striking at least a portion of the core inside the airfoil with the water jet and removing the core from inside the airfoil.

FIELD OF THE INVENTION

The present invention generally involves a method for manufacturing anairfoil.

BACKGROUND OF THE INVENTION

Turbines are widely used in industrial and commercial operations. Atypical commercial steam or gas turbine used to generate electricalpower includes alternating stages of stationary and rotating airfoils.For example, stationary vanes may be attached to a stationary componentsuch as a casing that surrounds the turbine, and rotating blades may beattached to a rotor located along an axial centerline of the turbine. Acompressed working fluid, such as but not limited to steam, combustiongases, or air, flows through the turbine, and the stationary vanesaccelerate and direct the compressed working fluid onto the subsequentstage of rotating blades to impart motion to the rotating blades, thusturning the rotor and performing work.

The efficiency of the turbine generally increases with increasedtemperatures of the compressed working fluid. However, excessivetemperatures within the turbine may reduce the longevity of the airfoilsin the turbine and thus increase repairs, maintenance, and outagesassociated with the turbine. As a result, various designs and methodshave been developed to provide cooling to the airfoils. For example, acooling media may be supplied to a cavity inside the airfoil toconvectively and/or conductively remove heat from the airfoil. Inparticular embodiments, the cooling media may flow out of the cavitythrough cooling passages in the airfoil to provide film cooling over theouter surface of the airfoil.

As temperatures and/or performance standards continue to increase, thematerials used for the airfoil become increasingly thin, making reliablemanufacture of the airfoil increasingly difficult. Specifically, theairfoil is typically cast from a high alloy metal, and the coolingpassages are often drilled or machined into the high alloy metal atprecise locations and in precise geometries after casting to optimizethe cooling media flow over the airfoil. For example, a water jet may beused to drill the cooling passages through the high alloy metal atparticular locations and angles to enhance the cooling media flow overthe outer surface of the airfoil. Although effective at accuratelydrilling small diameter holes through the high metal alloy, the waterjet may also introduce grit byproducts inside the airfoil that may bedifficult to completely remove. Alternately or in addition, the waterjet may inadvertently strike the interior of the airfoil on the oppositeside of the cavity causing damage inside the airfoil. The gritbyproducts inside the airfoil and/or damage to the interior of theairfoil may be difficult to detect during the finishing steps. As aresult, a method for manufacturing an airfoil that reduces or preventsthe introduction of grit byproducts into the airfoil and/or inadvertentdamages to the interior of the airfoil would be useful.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention are set forth below in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

One embodiment of the present invention is a method for manufacturing anairfoil that includes casting the airfoil around a core and creating ahole through a surface of the airfoil with a water jet. The methodfurther includes striking at least a portion of the core inside theairfoil with the water jet and removing the core from inside theairfoil.

Another embodiment of the present invention is a method formanufacturing an airfoil that includes casting a high alloy metal arounda core and penetrating a surface of the high alloy metal with a waterjet. The method further includes striking at least a portion of the coreinside the high alloy metal with the water jet and removing the corefrom inside the high alloy metal.

Those of ordinary skill in the art will better appreciate the featuresand aspects of such embodiments, and others, upon review of thespecification.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof to one skilled in the art, is set forth moreparticularly in the remainder of the specification, including referenceto the accompanying figures, in which:

FIG. 1 is a perspective view of an exemplary airfoil according to anembodiment of the present invention;

FIG. 2 is a plan view of a core for manufacturing the airfoil shown inFIG. 1; and

FIG. 3 is a cross-section view of the airfoil shown in FIG. 1 and thecore shown in FIG. 2 after casting according to an embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to present embodiments of theinvention, one or more examples of which are illustrated in theaccompanying drawings. The detailed description uses numerical andletter designations to refer to features in the drawings. Like orsimilar designations in the drawings and description have been used torefer to like or similar parts of the invention. As used herein, theterms “first”, “second”, and “third” may be used interchangeably todistinguish one component from another and are not intended to signifylocation or importance of the individual components. In addition, theterms “upstream” and “downstream” refer to the relative location ofcomponents in a fluid pathway. For example, component A is upstream fromcomponent B if a fluid flows from component A to component B.Conversely, component B is downstream from component A if component Breceives a fluid flow from component A.

Each example is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that modifications and variations can be made in thepresent invention without departing from the scope or spirit thereof.For instance, features illustrated or described as part of oneembodiment may be used on another embodiment to yield a still furtherembodiment. Thus, it is intended that the present invention covers suchmodifications and variations as come within the scope of the appendedclaims and their equivalents.

Various embodiments of the present invention include a method formanufacturing an airfoil. Referring now to the drawings, whereinidentical numerals indicate the same elements throughout the figures,FIG. 1 provides a perspective view of an exemplary airfoil 10 accordingto an embodiment of the present invention. As shown in FIG. 1, theairfoil 10 generally includes a pressure side 12 having a concavecurvature and a suction side 14 having a convex curvature and opposed tothe pressure side 12. The pressure and suction sides 12, 14 areseparated from one another to define a cavity 16 inside the airfoil 10between the pressure and suction sides 12, 14. The cavity 16 may providea serpentine or tortuous path for a cooling media to flow inside theairfoil 10 to conductively and/or convectively remove heat from theairfoil 10. In addition, the pressure and suction sides 12, 14 furtherjoin to form a leading edge 18 at an upstream portion of the airfoil 10and a trailing edge 20 downstream from the cavity 16 at a downstreamportion of the airfoil 10. A plurality of cooling passages 22 in thepressure side 12, suction side 14, leading edge 18, and/or trailing edge20 may provide fluid communication from the cavity 16 through theairfoil 10 to supply the cooling media over the outer surface of theairfoil 10. As shown in FIG. 1, for example, the cooling passages 22 maybe located at the leading and trailing edges 18, 20 and/or along eitheror both of the pressure and suction sides 12, 14. One of ordinary skillin the art will readily appreciate from the teachings herein that thenumber and/or location of the cooling passages 22 may vary according toparticular embodiments, and the present invention is not limited to anyparticular number or location of cooling passages 22 unless specificallyrecited in the claims.

The exemplary airfoil 10 shown in FIG. 1 may be manufactured using anyinvestment casting process known in the art. For example, FIG. 2provides a plan view of a core 30 that may be used to manufacture theairfoil 10 shown in FIG. 1. As shown in FIG. 2, the core 30 may includea serpentine portion 32 with a number of long, thin branches orprojections 34 that extend from the serpentine portion 32. Theserpentine portion 32 generally corresponds to the size and location forthe cavity 16 in the airfoil 10, and the projections 34 generallycorrespond to the size and location of the larger cooling passages 22through the trailing edge 20 of the airfoil 10. The core 30 may bemanufactured from any material having sufficient strength to withstandthe high temperatures associated with the casting material (e.g., a highalloy metal) while maintaining tight positioning required for the core30 during casting. For example, the core 30 may be cast from ceramicmaterial, ceramic composite material, or other suitable materials. Oncecast or otherwise manufactured, a laser, electron discharge machine,drill, water jet, or other suitable device may be used to refine or formthe serpentine portion 32 and/or projections 34 shown in FIG. 2.Additional cooling passages 22, for example, through the pressure side12, suction side 14, and/or leading edge 18, too small to bemanufactured by casting may be machined into the airfoil 10 aftercasting, as will be described later.

The core 30 may then be utilized in a lost wax process or other castingprocess as is known in the art. For example, the core 30 may be coatedwith a wax or other suitable material readily shaped to the desiredthickness and curvature for the airfoil 10. The wax-covered core 30 maythen be repeatedly dipped into a liquid ceramic solution to create aceramic shell over the wax surface. The wax may then be heated to removethe wax from between the core 30 and the ceramic shell, creating a voidbetween the core 30 and the ceramic shell that serves as a mold for theairfoil 10.

A molten high alloy metal 40 may then be poured into the mold to formthe airfoil 10. The high alloy metal 40 may include, for example,nickel, cobalt, and/or iron super alloys such as GTD-111, GED-222, Rene80, Rene 41, Rene 125, Rene 77, Rene N5, Rene N6, PWA 1484, PWA 1480,4^(th) generation single crystal super alloy, MX-4, Hastelloy X,cobalt-based HS-188, and similar alloys. After the high alloy metal 40cools and solidifies, the ceramic shell may be broken and removed,exposing the high alloy metal 40 that has taken the shape of the voidcreated by the removal of the wax.

FIG. 3 provides a cross-section view of the airfoil 10 and core 30 asshown in FIGS. 1 and 2, respectively, after casting according to anembodiment of the present invention. As shown in FIG. 3, the high alloymetal 40 has been cast around the core 30 to form the airfoil 10 aroundthe core 30. An apparatus 50 may direct a water jet 52 at the airfoil 10to create one or more holes 54 through a surface 56 of the high alloymetal 40. The holes 54 may be any size or diameter, and the water jet 52is particularly suitable for forming holes 54 having a size or diameterless than 1 mm which would otherwise be difficult to form by casting.After penetrating through the surface 56 of the airfoil 10, the waterjet 52 may then strike at least a portion of the core 30 inside theairfoil 10. In this manner, the core 30 prevents the water jet 52 fromtravelling across the empty cavity 16 and impacting and possiblydamaging the high alloy metal 40 on the other side of the cavity 16.

The water jet 52 may further include an abrasive material that enhancesthe rapid and precise penetration of the water jet 52 through thesurface 56 of the airfoil 10. In particular embodiments, the abrasivematerial may include one or more garnets, aluminum oxides, or othersuitable materials for cutting through the surface 56 of the airfoil 10.After penetrating through the surface 56 of the airfoil 10, the waterjet 52 and abrasive material may then strike at least a portion of thecore 30 inside the airfoil 10. In this manner, the core 30 prevents thewater jet 52 and abrasive material from travelling across the emptycavity 16 and impacting and possibly damaging the high alloy metal 40 onthe other side of the cavity 16. In addition, the core 30 may preventthe abrasive material from spreading or dispersing inside the cavity 16of the airfoil 10, facilitating easier removal of the abrasive materialafter use of the apparatus 50 is complete.

Once the desired holes 54 have been cut into the airfoil 10 or highalloy metal 40, the core 30 may be removed from inside the airfoil 10using methods known in the art. For example, the core 30 may bedissolved through a leaching process to remove the core 30 and anyabrasive material from inside the airfoil 10, leaving the cavity 16,cooling passages 22, and/or holes 54 in the airfoil 10.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A method for manufacturing an airfoil,comprising: a. casting the airfoil around a core; b. creating a holethrough a surface of the airfoil with a water jet; c. striking at leasta portion of the core inside the airfoil with the water jet; and d.removing the core from inside the airfoil.
 2. The method as in claim 1,further comprising creating the core from a ceramic material.
 3. Themethod as in claim 1, further comprising striking the surface of theairfoil with an abrasive material in the water jet.
 4. The method as inclaim 1, further comprising striking the surface of the airfoil with atleast one of garnet or aluminum oxide.
 5. The method as in claim 1,further comprising striking the portion of the core with at least one ofgarnet or aluminum oxide.
 6. The method as in claim 1, furthercomprising striking the portion of the core with an abrasive material inthe water jet.
 7. The method as in claim 6, further removing theabrasive material from inside the airfoil.
 8. The method as in claim 1,further comprising removing the core from the airfoil by leaching.
 9. Amethod for manufacturing an airfoil, comprising: a. casting a high alloymetal around a core; b. penetrating a surface of the high alloy metalwith a water jet; c. striking at least a portion of the core inside thehigh alloy metal with the water jet; and d. removing the core frominside the high alloy metal.
 10. The method as in claim 9, furthercomprising creating the core from a ceramic material.
 11. The method asin claim 9, further comprising striking the surface of the high alloymetal with an abrasive material in the water jet.
 12. The method as inclaim 9, further comprising striking the surface of the high alloy metalwith at least one of garnet or aluminum oxide.
 13. The method as inclaim 9, further comprising striking the portion of the core with atleast one of garnet or aluminum oxide.
 14. The method as in claim 9,further comprising striking the portion of the core with an abrasivematerial in the water jet.
 15. The method as in claim 14, furtherremoving the abrasive material from inside the high alloy metal.
 16. Themethod as in claim 9, further comprising leaching the core from insidethe high alloy metal.